LONDON People should be cautious about taking vitamin E supplements regularly because doing so can increase the risk of a certain type of stroke, an international team of scientists said on Friday.
Researchers from the United States, France and Germany reviewed existing studies of vitamin E and its effect on stroke and found that taking the vitamin increased the risk of hemorrhagic stroke, where bleeding occurs in the brain, by 22 percent, but cuts the risk of ischaemic stroke by 10 percent.
Ischaemic stroke accounts for around 70 percent of all cases and happens when a blood clot prevents blood reaching the brain.
"These findings suggest that the use of vitamin E may not be as safe as we have believed and is actually associated with some harm in the form of increased risk for hemorrhagic stroke," said Markus Schurks, of the Brigham and Women's Hospital in the United States, who led the study.
The researchers stressed the effects on absolute risk are small, with 0.8 more hemorrhagic strokes and 2.1 fewer ischaemic strokes per 1,000 people taking vitamin E.
This is equivalent to one ischaemic stroke being prevented for 476 people taking the vitamin, they said, and one extra hemorrhagic stroke for every 1,250 people taking it.
"While the risk is small ... we caution against widespread uncontrolled use of vitamin E," Schurks said in a statement.
Previous research has suggested that taking vitamin E has a protective effect against heart disease and around 13 percent of the U.S. population takes vitamin E as a supplement, the scientists said in their study published in the British Medical Journal.
Stroke is the most common cardiovascular problem after heart disease and kills around 5.7 million people worldwide each year.
For their analysis, the scientists studied nine trials that had investigated the effect of vitamin E on stroke in more than 118,000 people, half of whom were taking at least 50 mg daily of vitamin E and half of whom were taking a placebo or dummy pill.
None of the trials suggested taking vitamin E increased the risk for total stroke, but the researchers found there were stark differences when looking at individual types of stroke.
The analysis found there were 223 hemorrhagic strokes among people taking vitamin E and 183 such strokes among those taking a placebo, meaning the group taking the vitamin were 22 percent more likely to have this kind of stroke.
A total of 884 people taking vitamin E had an ischaemic stroke compared with 983 people taking a placebo, meaning people taking the vitamin were 10 percent less likely to have this form of stroke.
"Although the effects of vitamin E that are shown ... are both relatively small, hemorrhagic strokes generally have more severe outcomes," said Tobias Kurth, of France's Hospital de la Pitie-Salpetriere, who also worked on the study.
"Based on these findings, we suggest considering other preventive strategies to reduce the risk of stroke such as a well balanced diet, not smoking, being physically active and maintaining a normal weight."
(Editing by Jon Hemming)